It is known in the art to dimerize ethylene to butene and use the recovered butene for manufacturing butadiene. U.S. Pat. No. 3,728,415 to Arganbright discloses producing butenes by dimerizing ethylene with a catalyst including palladium oxide with molybdenum oxide or tungsten oxide and using the product for dehydrogenation to make butadiene.
Other references of interest include the following: U.S. Pat. Nos. 3,911,042 and 3,969,429 to Belov et al. which disclose titanium/aluminum catalyzed dimerization of ethylene and note the product is useful for making butadiene; U.S. Pat. No. 7,488,857 to Johann et al. which discloses coproduction of butadiene and butene-1 from butane; and United States Patent Application Publication No. US 2011/0288308 to Grasset et al. which discloses ethylene dimerization with titanium/aluminum catalyst.
It is proposed in Japanese Patent Publication 2011-148720 to manufacture butadiene from ethylene by way of dimerizing ethylene followed by oxidative dehydrogenation using specified catalysts to minimize impact of various impurities. The method proposed includes the following steps (I) and (II): a step (I) for producing n-butene essentially free of isobutene by dimerizing ethylene at a reaction temperature of 150 to 400° C. in the presence of a catalyst consisting of nickel, alumina, and silica having a nickel content of 0.0001 to 1 wt. %; and a step (II) for producing butadiene by performing an oxidative dehydrogenation reaction on the n-butene obtained in said step (I) with oxygen at a reaction temperature of 300 to 600° C. in the presence of a complex metal oxide comprising molybdenum and bismuth as essential ingredients.
Impurities such as isobutene associated with conventional processing are problematical as noted in the 2011-148720 Publication. Additional impurities such as trimer (C6), tetramer (C8), diolefin (butadiene, isoprene, and heavier diolefin) and acetylenic by-products of ethylene dimerization likewise present challenges to efficient operation of a butadiene manufacturing process. See also United States Patent Application Publication No. US 2014/0088332 of Rolland which relates to butadiene manufacture from ethylene using nickel and zirconium dimerization catalysts to make butenes as well as United States Patent Application Publication No. US 2014/0088331 also of Rolland which relates to butadiene manufacture from ethylene using nickel and titanium dimerization catalysts to make butenes.